Process for the extraction of metal pollutants from treated cellulosic biomass

Abstract

The present invention relates to a process for extracting oxidised metal pollutants from treated cellulosic or lignocellulosic biomass to recover the metal. The treatment also generates a cellulosic or lignocellulosic biomass which can to be used as a feedstock for biofuel, for making cellulose containing materials, and provides a source of other renewable chemicals.

The invention claimed is: 
     
       1. A process for the extraction of metal pollutants from treated lignocellulosic biomass, the process comprising
 (a) contacting the treated lignocellulosic biomass with an ionic liquid, said ionic liquid comprising an anion and an organic cation, wherein the contacting produces a cellulose-rich solid material and a liquid phase, wherein the liquid phase comprises a hemicellulose fraction, a lignin fraction, and metal pollutants, the anion is selected from the group consisting of chloride (Cl − ), acetate ([OAc] − ), and hydrogen sulfate (HSO4] − ) and the cation is selected from (i) a cation of general formula: 
 
       
         
           
           
               
               
           
         
         wherein X is N; and 
         A1 to A4 are each independently selected from H, an aliphatic, C3-6 carbocycle, C6-10 aryl, alkylaryl, and heteroaryl; or 
         (ii) a cation containing a nitrogen-containing heterocyclic moiety. 
       
     
     
       2. The process of  claim 1  wherein the cation is selected from (i) a cation of general formula: 
       
         
           
           
               
               
           
         
         wherein X is N; and 
         A1 to A4 are each independently selected from H, an aliphatic, C3-6 carbocycle, Co-10 aryl, alkylaryl, and heteroaryl. 
       
     
     
       3. The process of  claim 2  wherein at least one of A1 to A4 is H. 
     
     
       4. The process of  claim 1  wherein the organic cation is a protic organic cation. 
     
     
       5. The process of  claim 1  wherein the cation is an alkylammonium, an alcoholammonium, or a mixture thereof. 
     
     
       6. The process of  claim 5  wherein the cation is N,N-dimethyl-N-butylammonium ([DMBA] + ). 
     
     
       7. The process of  claim 1  wherein the cation containing a nitrogen-containing heterocyclic moiety is an imidazolium based cation or a mixture thereof. 
     
     
       8. The process of  claim 7  wherein the imidazolium based cation is selected from 1-ethyl-3-methylimidazolium ([EMIM] + ), 1-butylimidazolium ([HBIM] + ) and 1-methylimidazolium ([HMIM] + ). 
     
     
       9. The process of  claim 1  wherein the ionic liquid is selected from N,N-dimethyl-N-butylammonium hydrogen sulfate ([DMBA][HSO4]), 1-butylimidazolium hydrogen sulfate ([HBIM][HSO4]), 1-methylimidazolium chloride ([HMIM]C I), 1-methylimidazolium hydrogen sulfate ([HMIM][HSO4]), or triethylammonium hydrogen sulfate ([TEA][HSO4]), or mixtures thereof. 
     
     
       10. The process of  claim 1  wherein the organic cation is derived from its conjugate base, and wherein the ionic liquid comprises at least 5% molar excess of the conjugate base. 
     
     
       11. The process of  claim 1  wherein the ionic liquid is contacted with the biomass in the form of a composition comprising the ionic liquid and 10-40% v/v water. 
     
     
       12. The process of  claim 1  further comprising
 (b) separating the cellulose-rich solid material from the liquid phase. 
 
     
     
       13. The process of  claim 12  further comprising
 (c(i)) washing the cellulose-rich solid material at least once with a washing fluid that is the ionic liquid or an organic solvent miscible with the ionic liquid. 
 
     
     
       14. The process of  claim 13  further comprising
 (c(ii)) separating the cellulose-rich solid material from the washing fluid. 
 
     
     
       15. The process of  claim 12  further comprising
 (d) adding an anti-solvent to the ionic liquid obtained in (b) to precipitate the lignin. 
 
     
     
       16. The process of  claim 12  further comprising removing water from the ionic liquid after step (b). 
     
     
       17. The process of  claim 15  further comprising removing water from the ionic liquid after step (d). 
     
     
       18. The process of  claim 1  further comprising electrodeposition of the metal pollutant from the ionic liquid. 
     
     
       19. The process of  claim 18  wherein after the electrodeposition, the ionic liquid is re-used in step (a). 
     
     
       20. The process of  claim 13  further comprising electrodeposition of the metal pollutant from the ionic liquid, wherein after the electrodeposition, the ionic liquid is re-used in step (c(i)). 
     
     
       21. The process of  claim 1  further comprising saccharification of the cellulose containing solid residue obtained in step (a) to obtain glucose. 
     
     
       22. The process of  claim 12  further comprising saccharification of the cellulose containing solid residue obtained in step (b) to obtain glucose. 
     
     
       23. The process of  claim 14  further comprising saccharification of the cellulose containing solid residue obtained in step (c(11)) to obtain glucose. 
     
     
       24. A method of fractionating lignocellulosic biomass, the method comprising:
 (a) contacting the lignocellulosic biomass with an ionic liquid, said ionic liquid comprising an anion and a N,N-dimethyl-N-butylammonium ([DMBA] + ) cation. 
 
     
     
       25. The method of  claim 24 , wherein the ionic liquid is N,N-dimethyl-N-butylammonium hydrogen sulfate ([DMBA][HSO4]).